temperature is lowered. This is explained by the presence of second band close to the conduction band minima. Silane which is a common n type dopant in GaAs and other III-V systems is shown to behave like p type in GaInSb. P-n junction structures have been grown on GaSb substrates to fabricate TPV cells.
In some metal oxide semiconductor (MOS) processes, sodium contamination may occur during the formation of source/drain contact windows or during subsequent metallization. Once introduced, the sodium diffuses laterally at different rates along several paths, with the potential for ultimate metal oxide semiconductor field effect transistor (MOSFET) threshold voltage instability. For this study, sodium was ion implanted within the source/drain region of a MOSFET near the end of its fabrication sequence, and various temperature and bias/temperature stresses were applied to induce sodium diffusion. The sodium appears to be prevented from reaching the MOS gate by a barrier, which can only be surmounted by the application of a gate bias voltage. The sodium diffusion coefficient for reaching this barrier is about at 400°C.
The optical constants {epsilon}(E)[{equals}{epsilon}{sub 1}(E) + i{epsilon}{sub 2}(E)] of single crystal GaSb at 300K have been measured using spectral ellipsometry in the range of 0.3--5.3 eV. The {epsilon}(E) spectra displayed distinct structures associated with critical points (CPs) at E{sub 0}(direct gap), spin-orbit split E{sub 0} + {Delta}{sub 0} component, spin-orbit split (E{sub 1}), E{sub 1} + {Delta}{sub 1} and (E{sub 0}{prime}), E{sub 0}{prime} + {Delta}{sub 0}{prime} doublets, as well as E{sub 2}. The experimental data over the entire measured spectral range (after oxide removal) has been fit using the Holden model dielectric function [Phys.Rev.B 56, 4037 (1997)] based on the electronic energy-band structure near these CPs plus excitonic and band-to-band Coulomb enhancement effects at E{sub 0}, E{sub 0} + {Delta}{sub 0}and the E{sub 1}, E{sub 1} + {Delta}{sub 1} doublet. In addition to evaluating the energies of these various band-to-band CPs, information about the binding energy (R{sub 1}) of the two-dimensional exciton related to the E{sub 1}, E{sub 1} + {Delta}{sub 1} CPS was obtained. The value of R{sub 1} was in good agreement with effective mass/{rvec k} {center_dot} {rvec p} theory. The ability to evaluate R{sub 1} has important ramifications for recent first-principles band structure calculations which include exciton effects at E{sub 0}, E{sub 1}, and E{sub 2}.
Influences of facet degradation of Al-free InGaAsP-GaAs 940-nm laser diodes were studied at power densities well below catastrophic optical mirror damage level using photoluminescence (PL) during normal operation and after a rigorous burn-in procedure. The shift in the PL peak of the cladding layer of the device is used to calculate the temperature of the facet. Devices with different facet treatments: untreated electron beam evaporation, untreated ion beam deposition, unpumped and passivated facets were compared. The results indicate that the degradation of facet is more severe for untreated and unpumped facets as compared to passivated facets. The results were also compared with power measurements, which show that the drop in the power during the first 50 h of operation is nonexistent for passivated facet devices leading to the conclusion that photo-induced oxidation is the major cause of the degradation of the facet and thus oxide removal and surface passivation are crucial to make stable laser diodes.
Data on {approximately} 0.55 eV In{sub 0.72}Ga{sub 0.28}As cells with an average open-circuit voltage (Voc) of 298 mV (standard deviation 7 mV) at an average short-circuit current density of 1.16 A/cm{sup 2} (sdev. 0.1 A/cm{sup 2}) and an average fill-factor of 61.6% (sdev. 2.8%) is reported. The absorption coefficient of In{sub 0.72}Ga{sub 0.28}As was measured by a differential transmission technique. The authors use a numerical integration of the absorption data to determine the radiative recombination coefficient for In{sub 0.72}Ga{sub 0.28}As. Using this absorption data and simple one-dimensional analytical formula the above cells are modeled. The models show that the cells may be limited more by Auger recombination rather than Shockley-Read-Hall (SRH) recombination at dislocation centers caused by the 1.3% lattice mismatch of the cell to the host InP wafer.
A closed form computer program has been developed for the simulation and optimization of In{sub x}Ga{sub 1{minus}x}Sb thermophotovoltaic cells operating at room temperature. The program includes material parameter models of the energy bandgap, optical absorption constant, electron and hole mobility, intrinsic carrier concentration and index of refraction for any composition of GaInSb alloys.
Several measurement systems and techniques for the electrical and thermal characterization of thermophotovoltaic (TPV) cells are discussed. One computer controlled system measures the quantum efficiency of cells from 0.8 to 2.6 microns. A probe resistor is used to account for cells with low shunt resistances. In the second system, a production-style robot provides automated measurements of I-V characteristics under dark, blackbody, and flashed illumination conditions. The system measures the length and width of each cell, and calculates the open circuit voltage, short circuit current, fill factor, and maximum power for each cell. The mean and standard deviation of the measured parameters are also computed. The third system measures the overall cell efficiency by a calorimetric technique. Heat losses due to radiation, conduction, and convection are factored into the analysis method.
Low bandgap 0.55 eV (2.25 /spl mu/m cutoff wavelength) indium gallium arsenide (In/sub 0.72/Ga/sub 0.28/As) thermophotovoltaic (TPV) cells use much more of the long wavelength energy emitted from low temperature (<1200/spl deg/C) thermal sources than either Si or GaSb cells. Data are presented on a statistically significant number (2500) of these TPV cells, indicating the performance obtainable in large numbers of cells. This data should be useful in the design and modeling of TPV system performance. At 1.2 A/cm/sup 2/ short-circuit current, an average open-circuit voltage of 283 mV is obtained with a 60% fill factor. The peak external quantum efficiency for uncoated cells is 65% and is over 50% from 1.1 to 2.2 /spl mu/m. Internal quantum efficiency is over 76% in this range assuming an estimated 34% reflectance loss.
This report presents an assessment of the efficiency and power density limitations of thermophotovoltaic (TPV) energy conversion systems for both ideal (radiative-limited) and practical (defect-limited) systems. Thermodynamics is integrated into the unique process physics of TPV conversion, and used to define the intrinsic tradeoff between power density and efficiency. The results of the analysis reveal that the selection of diode bandgap sets a limit on achievable efficiency well below the traditional Carnot level. In addition it is shown that filter performance dominates diode performance in any practical TPV system and determines the optimum bandgap for a given radiator temperature. It is demonstrated that for a given radiator temperature, lower bandgap diodes enable both higher efficiency and power density when spectral control limitations are included. The goal of this work is to provide a better understanding of the basic system limitations that will enable successful long-term development of TPV energy conversion technology.
Industry 4.0 promotes digitalisation of manufacturing organisations into smart factories. Communication and connectivity of an operational data collection are required principal. OPC Unified Architecture and standards like ISA95 are key resources to develop automated interfaces between equipment and manufacturing execution system (MES). The target is to integrate complex equipment in a convenient way through the use of a companion specification, a dynamic address space and a OPC UA client characterisation process. Challenges are the reconciliation of the right programming languages, the integration of generic, domain agnostic, domain specific and equipment specific information models. This study describes the generic approach and demonstrates its applicability in a complex manufacturing environment, serving as a blueprint for other environments. The outlined concept is based on C#/LabView source-code developed for semiconductor back-end equipment, which interacts with an MES. The proposed system is validated for a final-testing-unit in the production of kW-class high-power laser diodes.
